The present invention relates to an adeno-associated virus vector suited to increase the immunogenicity of cells, a vaccine containing such a vector and the use of both.
It is known that in about 0.5% of cancer patients, e.g., those suffering from malignant melanomas, the tumor reverses completely. In many cancer patients, a control of the tumor also takes place, so that it remains in a stable condition over years. This may be because the immune system influences the course of the cancer.
Many attempts have been made to activate the immune system, and to detect and eliminate tumor cells. However, these attempts have not yet yielded satisfactory results.
It is an object of the present invention to provide a product by which the immune system can be stimulated with respect to tumor cells.
Adeno-associated viruses (AAVs) are single-stranded DNA viruses belonging to the Parvovirus family. AAVs require helper viruses, particularly adenoviruses or herpesviruses, for their replication. In the absence of helper viruses AAVs integrate into the host cell genome, particularly at a specific site on chromosome 19.
The genome of AAVs is linear and has a length of about 4680 nucleotides. It comprises two reading frames which code for a structural gene and a non-structural gene. The structural gene is referred to as cap gene. It is controlled by the P40 promoter and codes for three capsid proteins. The non-structural gene is referred to as rep gene and codes for the rep proteins, Rep 78, Rep 68, Rep 52 and Rep 40. The two former proteins are expressed under the control of the P5 promoter while the expression of Rep 52 and Rep 40 is controlled by the P19 promoter. The functions of the Rep proteins are determined inter alia by the control of replication and transcription of the AAV genome.
The present invention relates to an adeno-associated virus vector having a foreign DNA which codes for a protein increasing the immunogenicity of cells.
The present invention is based upon the finding that adeno-associated viruses (AAVS) are suited to transduce tumor cells.
An AAV vector according to the invention contains a foreign DNA which codes for a protein boosting the immunogenicity of cells.
The term xe2x80x9cAAV vectorxe2x80x9d refers to any AAV, i.e., virus particle, and the DNA thereof. The AAV vector may be present in wild-type or modified form. The latter also means that it comprises expressible E4 sequences, particularly the ORF6 of the E4 sequences, of adenovirus. Moreover, it may be a system of several components that provide individual or all functions of AAV and/or its DNA. Such a system comprises, e.g., a rep-negative AAV vector and means providing an AAV Rep protein. The AAV vector may be inserted in cells where it integrates into the genome or remains in episomal form.
The term xe2x80x9cforeign DNA coding for a protein boosting the immunogenicity of cellsxe2x80x9d encompasses any foreign DNA that may be integrated within an AAV vector and whose expression product can boost the immunogenicity of cells. Examples of a foreign DNA are genes whose expression products are lacking from or are down-regulated in tumor cells, e.g., MHC-I genes, genes coding for costimulatory molecules, e.g., B7 genes, such as B7.1 and B7.2 genes, genes coding for secretory immunostimulators, e.g., cytokine genes such as IL-2, interferon and GM-CSF genes, and genes that code for tumor-associated antigens, e.g., MAGE1, tyrosinases or viral proteins, e.g., E7 protein of human papilloma virus and EBNA3 protein of Epstein-Barr virus. It is preferred that the expression of the foreign DNA be controlled by a heterologous constitutive or inducible promoter such as a tissue-specific or tumor-specific promoter. Furthermore, the foreign DNA can be inserted at any position in the AAV vector. In this connection, in some embodiments, the foreign DNA is present in or is present in place of the rep gene. In addition, in some embodiments, several foreign DNAs are present in an AAV vector.
Conventional methods may be used to prepare an AAV vector according to the present invention. For example, an AAV vector can be prepared as a virus particle as follows: Two plasmids are provided wherein the first plasmid is an AAV plasmid that contains a foreign DNA, e.g. a gene for a B7 molecule, between the 5xe2x80x2- and 3xe2x80x2-ITR sequences of AAV. However, this plasmid referred to as pAAV-B7 does not code for the AAV Rep and AAV Cap proteins. These proteins are encoded by a second plasmid. The second plasmid contains an SV40 origin of replication. The second plasmid is referred to as pSV40oriAAV. Both plasmids are transfected into cells expressing an SV40 T antigen. Such cells are, e.g., COS cells. The SV40 origin of replication of pSV40oriAAV is activated by the T antigen, and the plasmid is replicated. A high expression of the AAV Rep and AAV Cap proteins is obtained. AAV vectors are obtained as virus particles by infection of the COS cells with a helper virus, e.g., adenovirus. The titer is between 106-109 virus-particle/ml.
The immunogenicity of cells can be increased by means of such an AAV vector. In some preferred embodiments, an AAV vector coding for several proteins boosting the immunogenicity of cells is provided. In some other preferred embodiments, several AAV vectors coding for differing proteins boosting the immunogenicity of cells are provided. The increase in immunogenicity can be achieved with cells of any kind, particularly tumor cells or pre-tumor cells such as HPV-transduced cervical cells.
The cells can be transduced with the AAV vector by conventional methods. If the AAV vector is present as a virus particle, the cells may be infected with the viral particle. However, if the AVV vector is present as DNA, it is advisable to transfect the cells therewith. For example, electroporation and lipofection may be used as transfection techniques. The cells can be present in an organism, or the cells to be transduced can also be isolated from an organism, transduced outside the organism and be introduced into the organism again. Such cells are referred to as autologous cells. Moreover, allogenic cells may be used for the transduction. In this connection, it is favorable for the allogenic cells to belong to a HLA type corresponding to the organism. The person skilled in the art readily understands methods of providing cells with a certain HLA type. In addition, it is preferred for the cells, particularly tumor cells or pre-tumor cells, to be inactivated before introducing them again into the organism. Conventional methods such as irradiation may be used for this purpose.
Cells that are transduced outside an organism may also be co-cultivated with autologous and/or allogenic nuclear blood cells, particularly lymphocytes, based on the organism. The nuclear blood cells may be stimulated by this, and they may be introduced into the organism as such or together with the transduced cells.
The present invention also relates to a vaccine that comprises an AAV vector according to the invention. The vaccine may further comprise conventional auxiliary agents such as buffers, diluents, carriers, etc. In some embodiments, the AAV vector codes for several proteins boosting the immunogenicity of cells. In some other embodiments, several AAV vectors are provided that code for differing proteins boosting the immunogenicity of cells. In some preferred embodiments, the vaccine comprises further substances boosting the immunogenicity of cells, particularly tumor-specific antigens. These antigens may be present, e.g., in the form of peptides, particularly synthetic peptides. The antigens may also be present in the form of expression plasmids encoding them that can also code for HLA molecules. It is especially favorable for the vaccine to also contain the cells transduced by the AAV vector and/or the nuclear blood cells stimulated by these cells. In particular, it is preferred that the cells be inactivated. Moreover, it is preferred that the vaccine contain a replication-defective adenovirus whose E4 sequences are operational. Expressible E4 sequences may also be present on a vector or an E4 protein. It is preferred that the vaccine contain a substance supporting DNA replication. This may be, e.g., hydroxy urea, a topoisomerase inhibitor or a DNA synthesis inhibitor in a minor amount. It may also be favorable to irradiate the vaccine, e.g., X-ray or gamma irradiation.
The present invention provides methods to transduce cells, particularly tumor cells or pre-tumor cells, more particularly freshly isolated tumor cells, with great efficiency. A transduction efficiency of 85 to 95% may be obtained. Therefore, the most differing cells of a tumor may be transduced so that the entire antigen profile of the tumor is detected and clonal selection is prevented. Moreover, transduction of the individual cells may be achieved with a small number of AAV vector molecules such as 10 to 20 molecules per cell. Therefore, the transduction does not cause a cytopathic effect. Hence, the immune system recognizes the transduced cells and further cells having an equal antigen profile and can eliminate them.
Thus, the present invention is suited to boost the immunogenicity of cells, particularly tumor cells or pre-tumor cells. As a result, the present invention is adaptable for use in vivo and/or ex vivo gene therapy of serious diseases such as cancers, including malignant melanoma and cervical carcinoma.
The invention is further explained by the following examples. These examples are provided only to further illustrate the present invention.